Cosmetic formulations (alternatively called compositions) or like materials can be topically applied to a surface, such as skin, in a variety of different physical forms, using a variety of different dispensers (applicators) of which one combination comprises a stick, made from firm, solid material, by which is meant a solid integral bar that retains its shape if removed from the dispenser. This is to be contrasted with soft solids that do not retain their shape if removed from the dispenser.
A dispenser for sticks conventionally comprises a barrel that is open at one end within which a platform (sometimes alternatively called an elevator, godet or piston) can be advanced towards the open end. Such a dispenser often comprises a mechanism for advancing and commonly, though not always, also for retracting the platform and usually has a cap for the open end to reduce substantially loss of volatile substances from the stick composition.
Herein, although the discussion of dispensers is made explicitly in relation to dispensing cosmetic stick formulations, including in particular antiperspirant and/or deodorant formulations, and is of particular benefit to such cosmetic formulations, it will be recognised that the problems and their solution can apply mutatis mutandis to like materials. Such materials can include, if desired, therapeutic or curative stick formulations, intended for application to humans or animals.
In use, a fraction of the stick is conventionally advanced through the open end of the barrel, i.e. its top and is wiped across the surface to which the composition is to be applied. This imparts a lateral force to the stick which could dislodge the stick from the platform unless it is adhered to the upper face of the platform. Up herein indicates towards the open end and upper closer to the open end, whereas down indicates away from the open end, i.e. towards the bottom (otherwise referred to as base) of the barrel and lower further away from the open end, i.e. closer to the base. The terms top and bottom are employed correspondingly in regard to the other components of the dispenser, such as the platform, the rotor wheel and the spindle, and parts of such components. Herein, outward indicates towards the exterior of the dispenser or of a part of a component when fitted within the dispenser and is usually employed in relation to a lateral part. Inward indicates away from the exterior of the dispenser, commonly laterally.
When stick dispensers were first introduced, they employed a generally solid platform with a central threaded aperture, having a flat or possibly domed upper surface. However, dispensers having a solid platform must be filled from the top, through the open end of the barrel, which runs the risk of spillage if the amount of material discharged into the barrel is not controlled very closely. Moreover, the top surface of the stick material can present a rough appearance that does not appeal to consumers, so that a subsequent processing step is needed to create a smooth and acceptable appearance. Consequently, stick dispensers that are able to be filled through the base of the dispenser have been proposed, sometimes called bottom fill, as in for example U.S. Pat. No. 4,605,330 and other subsequently. In such dispensers, the rotor wheel that is mounted in the base of the barrel defines a central aperture spanned by a cross spoke or spokes bearing the spindle and the platform likewise defines an aperture or apertures through which the stick material can flow. Typically, the barrel is inverted for filling through the base and its open end is closed by a former or temporarily by a puck during the filling operation. The platform can comprise a solid lateral plate having a rim that contacts the barrel sidewall and one or more apertures or may be skeletal. By skeletal in this context is meant a structure that comprises a plurality of upstanding walls, defining apertures in between, though some, but not all, of the skeletal structure may be spanned by a lateral sheet. Typically, a skeletal platform comprises a rim wall, that may be continuous or intermittent, and several designs also comprised a number of radiating spokes from a central hub.
A number of problems have been identified in respect of stick dispensers in general and bottom fill stick dispensers in particular. It has been found that many cosmetic compositions, including in particular solid antiperspirant or deodorant compositions, do not adhere particularly strongly to a simple plain surface of the platform, which is typically made from a thermoplastic, so that subsequently, many inventors have sought to modify the platform shape to assist the composition to key with the platform. Adaptations to the platform have included a flanged tower extending above the main upper surface of the platform, as in U.S. Pat. No. 4,915,528 and U.S. Pat. No. 6,960,208, but that is not liked by users because of its shape. A tower, with or without flanges tends to dig into the skin to a much greater extent than does a flat or domed platform upper surface and is accordingly uncomfortable. Accordingly, it is considered preferable to employ a skeletal platform, but that has the disadvantage of having to be deeper than a simple plate, so that the length of the barrel has to be increased to accommodate it. It would be beneficial to identify a means of reducing the depth of the skeletal platform whilst at least maintaining previously enjoyed extent of adherence of the stick material to the platform during use.
The stick material is subjected in use to lateral forces and in advancement or retraction to longitudinal forces. The design of the platform needs to take both sets of forces into account. Moreover, it has become generally recognised that the world needs to conserve its resources better, so that a new design should strive to meet the objective of maintaining adherence whilst reducing the amount of construction material to make the platform. However, the inventors have further realised that less platform material could equate to thinner elements in a skeletal platform, but thinness increases the risk of flexing, and flexing results in creating fault lines at the junction of stick material and platform element. Thus, although the problem may be easy to state, the solution is not easy to obtain.
A further problem associated especially with bottom filling of stick dispensers, which commonly occurs under gravity or at a low pump pressure, is how to control the flow so as to ensure even filling, avoid air pockets and wasteful internal splashing and disruption to the flow as a result particularly of the material encountering the mounting for the spindle and/or particularly elements within the platform en route to the body of the barrel. Such needs complicate any solution to maintaining stick adherence and/or reducing the use of resources.
A skeletal platform means that the lower surface of stick can lose some of the carrier liquid that has been gelled to form the solid stick. Such drying out of the stick material often weakens the adherence of the material to the platform so that one or more seals are incorporated at the mounting of the wheel at the base of the barrel and of course the aperture in the wheel is normally plugged. However, seals typically bridge parallel surfaces of the elements forming the mounting of wheel at the base, and this likewise introduces dead space in the barrel. The inventors have recognised that it would be desirable to identify means to reduce the dead space without sacrificing the adherence of the stick material to the platform.
It would be inherently desirable to devise a platform that is capable of exhibiting reduced retention of stick composition therewithin when the platform reaches the open end of the barrel.
One means for reducing the proportion of stick material retained within the platform has been disclosed in EP0650336, published in 1994, which employs a design that employs a platform with a solid base and an upstanding rim. In the design therein, the platform comprises a well which is filled by the stick composition. The rim is halted when it reaches the open end of the dispenser whereas the base continues to be advanced, thereby sweeping the composition out of the well. However, such a design requires an interior stop to be provided at the open end of the barrel. Its function is to halt the upward advancement of the rim, but by the same token, it impedes insertion of the platform into the barrel through its open end. It is possible to contemplate a design of the stop coupled with distortion of the barrel open end sufficient to permit insertion of the platform, but such a combination of stop design plus barrel distortion that permits insertion also runs a severe risk that the same extent of distortion would prevent the stop from functioning. Not surprisingly, this design seems not to have been commercialised in the 15 years or so since it was devised. It can be deduced that an alternative solution is needed.
Accordingly, the problem remains to find a practical solution to the problem of how to reduce the loss of stick material within a skeletal platform whilst retaining acceptable adhesion of the material to the platform.
Other and further problems associated with bottom fill stick dispensers relate to the dead space in between the base of the barrel and the platform. Such space contributes to the weight of the package and in particular the weight of plastic needed to make the dispenser.
It is an object of the present invention to at least alleviate one or more of the disadvantages or problems with bottom-fill dispensers identified hereinabove.
Other and further objects of the invention may become apparent during the following discussion of the invention.